Transcript Monday Oct
19 October 2011 This Week in Physiology: Lab: Visual System Part 2, Somatosensory Data Collection Vestibulocochlear system PPT Lectures: Ch. 9 Muscle Physiology Next Week in Physiology: Lab: Frog muscle physiology Lectures: Ch. 10 Control of Body Movement Abstracts due Friday Instructions on Website! About midterm grades….. About Take Home portion of Test 1 1QQ # 19 Write a question that you were prepared to answer today and provide the answer to that question. A more challenging/sophisticated/thoughtprovoking question with its correct answer earns more points than a simple memorization-type question. S1 Muscle kinetics Link to cytosolic calcium concentration, release, and reuptake? S2 Fig. 09.16 S3 Fig. 09.20 Why does this plateau? So….. Tension produced by a single myofiber varies depending on frequency of Action Potentials. S4 Muscle Metabolism • Classification of Myofiber types – Speed of myosin ATPase – Metabolic sources of ATP – Fatigability S5 Classes of Myofibers based on Twitch Duration Each muscle fiber express only one of two different myosins isozymes: • Fast twitch = rapid hydrolysis of ATP means crossbridges cycle faster • Slow twitch = slower hydrolysis, isozyme catalyzes the reaction slower Myosin isozymes not modified by athletic training! S6 Classes of Myofibers based on Metabolic and Enzyme profiles • Oxidative: at peak activity rely on full aerobic cellular respiration – many mitochondria, enzymes for oxidative phosphorylation, numerous capillaries, lots of myoglobin (red) • Glycolytic: at peak activity rely on glycolysis – few mitochondria, many glycolytic enzymes, large store of glycogen, fewer capillaries, little myoglobin (white) Metabolic profiles CAN BE modified by athletic training! S7 3 Sources of ATP in muscle Powerstroking & Disconnecting crossbridges Creatine phosphate, then oxidative phosphorylation (OP) from glycogen, then OP from blood glucose, then blood fatty acids. If intense, switch to glycolysis… then take a breather… oxygen debt S8 A 1998 Review on the Use of Creatine as a Nutritional Supplement S9 Type I Type II A Fig. 09.03 Type II B S 10 S 11 Type I What are the causes of fatigue? Type IIA Depends on the type of activity… Type IIB S 12 Causes of fatigue • High intensity, short duration exercise – Conduction failure in t-tubules – Lactic acid accumulation – Accumulation of ADP and inorganic phosphate • Low intensity, long duration exercise – – – – As above, and Depletion of muscle glycogen Low plasma glucose (hypoglycemia) Dehydration • Control pathways: “willpower” – Common in couch potatoes S 13 So what are the ways a muscle (consisting of many myofibers) increases tension? S 14 Fig. 09.13 Motor unit = a single somatic motor neuron and all the muscle fibers in innervates S 15 But each motor unit has myofibers of the same type: I or IIA or IIB. S 16 Increasing tension in a whole muscle • Frequency of stimulation of motor neuron • Activate larger motor units • Recruitment: activate more motor units • These factors also influence actual tension – Fiber length (length-tension) relationship – Fiber diameter – Level of fatigue (state of activity) S 17 Fig. 09.26 Relationship between recruitment and motor unit type The Size Principle Size of somatic motoneuron cell body